Add Hydroconsolidation Region

Soil collapse, or hydroconsolidation, may occur with certain soil types (e.g. loose clayey sand) - when exposed to water, the clay bonds break causing significant volume reduction. The amount of collapse depends on the stress. At very low stresses, these soils may actually experience swelling. See the Settle3 Theory document for further details.

The Add Hydroconsolidation Region option allows you to define a region in which hydroconsolidation may occur.

To define a hydroconsolidation region:

1. Select Add Region (Hydroconsolidation) from the Groundwater tab.
2. You will see the Hydroconsolidation Region Properties dialog.
• Specify the Wetting Stage of the hydroconsolidation region. By default the wetting stage will be defined by the elevation of the water table. Or you can choose a wetting stage which is independent of the water table elevation. See below for details.
• Specify the top and bottom depth of the region. By default it is assumed that the region covers the entire vertical extent of the model. However, you can define any elevations within the soil profile as the top and bottom depth of the region. The top and bottom do not necessarily have to correspond to the elevation of soil layers.
3. Select OK in the dialog, and you will be prompted to enter a polygon defining the hydroconsolidation region. In the Plan View, enter the vertices of a closed polygon which defines the boundary of the hydroconsolidation region, as described in Entering Coordinates.
4. The hydroconsolidation region will be added to the model, and displayed in both the Plan View and 3D View.

Hydroconsolidation Properties

A hydroconsolidation region only defines the region within which hydroconsolidation will take place. After a region is defined, you must also define the hydroconsolidation properties for the relevant soil layers within the hydroconsolidation region. This is done with the Hydroconsolidation Properties dialog.

For details see the Hydroconsolidation Properties topic and the Settle3 Theory document.

Wetting Stage

The wetting stage of a hydroconsolidation region determines when the hydroconsolidation will take place. There are two possible options - Use Water Table, or choose a particular stage.

• If the Wetting Stage = Use Water Table, then hydroconsolidation will occur only when the elevation of the water table is raised within the hydroconsolidation region. Hydroconsolidation will only occur for soil regions which were previously above the water table (dry), and are then below the water table. This may occur in multiple stages (e.g. if the water table is raised in increments over a number of stages).
• If the Wetting Stage = (a particular stage), then the entire hydroconsolidation region is considered to be fully saturated (e.g. flooded) at that particular stage, and this will occur independently of the water table elevation (i.e. the region will be considered to be saturated even if it is above the water table). In this case, hydroconsolidation of the entire region will occur at the specified stage.

In either case, hydroconsolidation settlement can only occur once at a given location, the first time the material becomes saturated.